An engine is a device or machine whereby using a specific process, energy is transformed from one form, i.e. thermal energy or heat, to another form. i.e. kinetic energy.
Relevance of Efficiency
The efficiency of such a process and the device or machine to realise the process is of importance because engines are used in such large numbers worldwide that they have an influence on world climate and therefore inefficiency poses a real threat to nature and thus mankind. Also the cost factor for creating kinetic energy from heat energy is an important factor in an economy thus the efficiency of such processes is important.
Using Evaporation of Liquids
Most liquids can evaporate. By heating the liquid beyond its specific evaporation-temperature the liquid changes from a liquid state to a gaseous state. In the gaseous state the fluid is commonly called gas, steam or vapour depending on the type of liquid.
Each liquid has its specific evaporation temperature for ambient or standard-condition often referred to as ‘STP’. One of the most common standard conditions are 25 degrees Centigrade and 100 kPa (=1 bar). Under standard conditions one liter of water will evaporate to 1,673 liters of steam. If 1,673 liters of steam condenses and forms the liquid state of water, the volume will be reduced to one single liter—about 1600 times less.
A process of evaporation of water will start under standard condition of 100 kPa at 100 degrees Centigrade. If the pressure is higher the process of evaporation will start at a proportionally higher temperature. For each pressure there is a specific temperature at which evaporation takes place. The value of this temperature can be looked up in specific steam tables for water and many other fluids. Water for example remains a liquid at 200 degrees Centigrade when the pressure is at or above 1,512 MPa.
When a liquid changes from the liquid state to the gaseous state additional energy has to be supplied for the evaporation process that is not used to increase the temperature but to enable the molecules to separate and form a gas. This energy, which is referred to as “evaporation heat” or “latent heat” because it doesn't heat the liquid, has a different specific value for each liquid. For water it is 2,257 kJ per kg water.
In order to produce (dry) steam with a temperature of 200 degrees Centigrade it is necessary to supply the energy needed for the increase of temperature, i.e. around 735 kJ per kg water, plus the energy for the evaporation heat, i.e. 2,257 kJ per kg water. From the total amount of energy that had been added to the water to produce steam of 200 degrees Centigrade only 24.5% of the energy in the hot steam can be used when the hot steam cools down. 75.4% cannot be released in the form of heat. The same calculation for steam with a temperature of 800 degrees Centigrade needs 3,255 kJ per kg water plus the 2,257 kJ for the evaporation heat. Together this is 5,512 kJ per kg water. In this case around 60% of the heat that had been introduced into the water can be used. In both cases the same amount of energy for the evaporation has been added.
But in the second case the percentage that can be used is higher due to a higher end-temperature. Therefore steam processes like turbines in power stations that use the Rankine process use the highest possible temperature of the steam in order to achieve better efficiencies.
If an engine can use the pressure of the process fluid, e.g. in the case of a steam engine or steam turbine, the pressure of the steam that enters the expansion chamber until complete expansion, it can use only use the percentage of the heat that does not include the evaporation heat. For lower temperatures as in the example above shown 75% of the heat energy in the process fluid is lost because in engines or turbines known today the enthalpy of condensation cannot be transformed in the process into kinetic energy. This loss is in addition to mechanical and other losses. It is for this reason that the Rankine process or Clausius-Rankine process, which are used today for most engines that work with a heated process fluid or steam, are operated at the highest possible starting temperature to keep the percentage of the amount of the (lost) heat of vaporisation as low as possible.
The Term “Engine”
As used herein the term “engine” is used to describe a device as hardware that is designed to allow one or more specific processes that are unique for the purpose of transforming energy from one form to another to be realised. All known engines today—with the possible exception of the “Six-stroke engine”—are based upon and only use one single process to transform thermal energy into kinetic energy.
Engine Design
There is a fundamental difference between a specific process and the hardware design of an engine. This becomes clearer with the example of the internal combustion engine using the four-stroke process, as is commonly used today in most cars. The four-stroke process is in most cases realised in a piston engine, but it can also be realised in a Wankel rotary engine. Thus there is the same process but two fundamentally different designs of the engines. The opposite is also true. In piston engines different processes can be realised. For example consider the Lenoir gas engine with a two stroke process without compression, the four stroke process with compression, and as realised in the six-stroke engine (The development of piston engines over the years can be followed in the patent literature by considering, for example, U.S. Pat. No. 1,333,176 to L. H. Dyer from 1920 and U.S. Pat. No. 7,549,412 to S. Singh from 2006) also as a combination of a uniflow-steam-engine-process with a conventional four-stroke-engine process. From this it is clear that a new engine-process can be realised in existing engine concepts or designs.
Rotary Engines
Nearly all rotary engines share their basic design with rotary lobe or rotary piston gear pumps. These kinds of pump come in many variations and most of these variations can also be used for an engine design. The patent U.S. Pat. No. 904,749 to C. A. Bender from the year 1908 shows such a design that is used as a steam engine. In Bender's engine steam is expanded in a bent cuboid expansion chamber that is closed at its two face-sides by small rotors with a recess to allow a rotor blade that acts as a piston to pass through this recess. In many other similar rotary engines the task of allowing the continuous creation of closed expansion chambers is carried out by radially moving flaps that open and close to move into and out of the path of the piston-like rotor blade. There are many more similar designs—probably several thousands—for either steam engines or also other forms of engines, pumps and compressors.
It is a purpose of the present invention to provide a new process for converting thermal energy to kinetic energy with very high efficiency.
It is another purpose of the present invention to provide engines that are designed to operate using the new process for converting thermal energy to kinetic energy with very high efficiency.
Further purposes and advantages of this invention will appear as the description proceeds.